Effects of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride on the microhardness of enamel treated with a bleaching agent: ex vivo

Objective: The aim of this study was to compare the effects of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and 1.23% acidulated phosphate fluoride (APF; pH 3.5) on the microhardness of enamel treated with a bleaching agent. Materials and Method: Enamel slices (n=32; 2×4 mm) were obtained from 8 mandibular permanent molar teeth. Specimens were embedded into acrylic resin blocks with the enamel surfaces facing upwards. Vickers microhardness (VHN) values of the specimens were recorded at baseline. The specimens were randomly divided into 4 experimental groups, and the experimental designation was as follows: Group 1: no treatment (control), Group 2: 35% hydrogen peroxide (HP), Group 3: HP + CPP-ACP, Group 4: HP + APF application. After treatments, VHN values were measured and recorded again. Specimens were stored in artificial saliva at 37 °C for 1 week. After 1 week second application was done and VHN of the specimens was registered once more. Data were statistically analyzed with ANOVA and Tukey post hoc tests. Values obtained at baseline, and first and second applications were compared using paired samples t-test (α=0.05). Results: In inter-group comparisons, no statistically significant difference in the enamel microhardness values was found between the baseline, and first and second applications (p>0.05). In intra-group comparisons, again, no statistically significant difference in the enamel microhardness values was found between the baseline, and first and second applications (p>0.05). Conclusion: According to the limitations of this study it can be concluded that neither the HP application nor the CPP-ACP or APF application after HP had any significant effect on the enamel microhardness.